Handling pulverulent catalyst in hydrocarbon conversion and catalyst regeneration operations



Oct. 17, 1950 w, KREBS HANDLING PULVERULENT CATALYST IN HYDROCARBONCONVERSION AND CATALYST REGENERATION OPERATIONS 35 Sheets-Sheet 1 FiledJuly 12. 1941 We 1? 7'4 TOP. CA5 OUTLT F/NELY DE l PRECIP/TATOR ousrMIXED WITH 8 F/NELY D/V/DED SOL/D YCLONE 321% RA ran FIG-1 REGENERATIONGAS AND F/NELY DIV/0E0 aoL p INLET 58 A IIOPPEZ STEA M INLE T I 6J0?FEED W WM M KREBS 2,526,486

HYDROCARBON CONVERSION 0N OPERATIONS 3 Sheets-Sheet 2 Oct. 17, 1950' R.w.

HANDLING PULVERULENT CATALYST IN AND CATALYST REGENERATI Filed July 12.1941 YCLONE JEPARATOR I 88 l llOfPEE T PkEC/P/TA 7'02 4113012 7551) mazrj] k .138 pa [122 Oct. 17, 1950 R. w. KREBS 2,526,435 HANDLINGPULVERULENT CATALYST IN mnaocmon CONVERSION AND CATALYST REGENERATIONovm'rxous Filed July 12, 1941 3 Sheets-Sheet 3 eye 1. 0 NE SAEPARA 1'07?.SOl-IDS AND C YC L 0 NE I 168 196 174 1 Fm l] a L coo/.212 t I fl/07PE2 race/PITA 1'02 the products of Patented Oct. 17, 1950 areHANDLING- PULVERULENT CATALYST IN HYDROCARBON CONVERSION AND CATA- LYSTREGENERATI ON OPERATIONS Robert W. Krebs, Baton Rouge, La., assignor toStandard, Oil Development Company, a corporation of Delaware ApplicationJuly 12, 1941, Serial No. 402,193

15 Claims.

This invention relates to conveying or handling powdered or finelydivided materials and \more specifically relates to conveying powderedor finely divided catalyst particles in the catalytic treatment ofhydrocarbons.

In the catalytic treatment ,of hydrocarbons such as the catalyticconversion of hydrocarbons either to higher or lower boilinghydrocarbons, one method comprises mixing finely ground or powderedcatalytic material with hydrocarbon vapors heated to conversiontemperature, passing the mixture through a reaction zone wherein it ismaintained for a sufficient time to effect the desired extent ofconversion of the hydrocarbons and then separating the resulting mixtureinto solid catalyst particles and reaction products in vapor form.Preferably the catalyst particles are separated from the reaction prod-.ucts or products of conversion while the products of conversion are atan elevated temperature so that there is substantially no condensationof any constituents and a dry separation is effected between thevaporous constituents and the solid particles. 7

In order to recover most of the powdered catalyst particles preferably aplurality of separating zones or means is provided. For example,conversion and catalyst particles are first passed through a separatingmeans such as a cyclone separator to separate a large part of thepowdered catalyst. Then the separated vapors are passed through anotherseparating means such as a cyclone separator to separate furtherquantities of powdered catalyst from the vapors. If desired, theseparated vapors may then be passed through an additional separatingmeans such as a cyclone separator and/or through an electricalprecipitator to remove substantially all of the powdered catalyst fromthe vapors.

After the catalyst particles have been passed through the reaction zone,it is necessary to regenerate them to remove deposited carbonaceousmaterial resulting from the conversion in the reaction zone. Thecatalyst particles are preferably regenerated as a suspension in a gassuch as steam or flue gas free of oxygen and passed through aregeneration zone in the presence of air or oxygen to burn oh? thecarbonaceous deposit. It is essential that the temperature be controlledduring regeneration in order to prevent sintering or fusing of thecatalyst particles. After regeneration, the catalyst particles areseparated from the regeneration gases by a plurality of separating meanssuch as cyclone separators and the last separating means is preferablyan electric precipitator to remove catalyst fines.

In each succeeding separating step the recovered catalyst particles aresmaller, that is, the largest particles are removed from the vapors orgases in the first separating stage and the smallest particles areremoved in the last separating stage. The separated catalyst particlesare allowed to drop into a hopper or the likeafter which they are usedfor any further treatment desired. It has been found that it isdifiicult te convey the very fine particles separated in the last stageor latter stages of separation, par= ticularly the very fine particlesseparated in the electric precipitator. These fine particles have atendency to bridge adjacent the outlets of hoppers and do not flowthrough pipes very readily.

In another process for the catalytic treatment of hydrocarbons thecatalyst particles in finely divided form are aerated or fluidized, thatis, they are mixed with the gas and the resulting aerated mass acts as afiuid which can be fed to a reaction zone by the hydrostatic head ofpressure produced by a column of the fluidized catalyst. Here again ithas been found'that the exceedingly fine catalyst particles separated inan. electrical precipitator or in the last stages of cyclone separationdo not aerate and it has not been possible to aerate these fineparticles to convey them to a desired point or to return these fineparticles to a hopper as an aerated stream.

According to my invention, the catalyst fines or other exceedingly fineparticles which are hard to aerate and which tend to bridge incontainers or pipes are mixed with a small amount of coarse particles ofthe same or other material to facilitate the flow of the fine particlesthrough pipes and from containers or hoppers.

In one form of the invention, solid particles suspended in a gas arepassed to a first separating means to separate solid particles from thegas. The separated particles are introduced into a main hopper. The gasseparated from the solid particles in the first separating means stillcontains solid particles and it is preferably introduced into a secondseparating means for separating an additional quantity of solidparticles from the gas. The solid particles are delivered to the samehopper into which the particles from the first separating means aredelivered.

The gases from the second separating means still contain solid particlesbut the solid particles are much smaller than the particles removed inthe first and second separating means. A third separating means may beused. The fine ascents particles remaining in suspension after passingthrough the separating means are preferably separated in an electricprecipitating means. These separated fine particles, however, are moredifllcult to handle than the coarser particles and they have a tendencyto bridge the outlet from the bottom of the electric precipitating meansand also these fine particles do not flow as readily as the larger. orcoarser particles. In order to handle these particles more easily, aportion of the coarser particles from the main hopper is suspended ingas and introduced into the lowerpart of the electric precipitatingmeans for admixture with the fine particles. The resulting mixture hasbetter flow characteristics than the fine particles and also may befluidized whereas it is practically impossible to fluidize the fineparticles from an electric precipitating means. The mixture of flneparticles and coarser particles is returned to the main hopper.

In another form of the invention the solid particles in a gaseoussuspension are introduced into a first separating means to separate alarge percentage of the solid particles from the gas, the gas passing toa second separating means. The separated solids in the first separatingmeans are introduced into a main catalyst hopper. The second separatingmeans separates an additional quantity of solid particles from the gas.The solid particles from the second separating means are introduced intothe main hopper and the gas is preferably passed to an electricprecipitating means for separating fine particles from the gas.

The fine particles separated in the precipitating means are difficult tofluidize or aerate and in addition have a tendency to bridge over theoutlet of containers from which the fine particles are withdrawn. Inorder to improve the flow characteristics of the fine particles, aportion of the coarser solid particles from the main hopper areintroduced by gravity directly into the lower portion of'the electricprecipitating means. The resulting mixture of fine and coarser particleshas better flow characteristics than the fine particles and also may beaerated to form a fluidized stream.

The mixture is introduced into a standpipe where it is maintained in afluidized r aerated condition and then passed to one of the separatingmeans for separating solids from gas and the solids are introduced intothe main hopper. In another form of the invention the gaseous suspensionof the solid particles is passed through a plurality of separating meansas above described and the solid particles are introduced into a mainhopper. The gases containing the fine solid particles are introducedinto an electric precipitating means for separating the fine particlesfrom the gas. In this form of the invention all of the coarser or largersolid particles from the main hopper are introduced into the lowerportion of the electric precipitating means or into the hopper directlybelow the electric precipitating means for admixing all of the coarsersolid particles with the fine particles. The mixture of coarser and fineparticles is then withdrawn from the bottom of the electricprecipitating means and from there withdrawn and carried to any desiredpoint.

In the catalytic conversion of hydrocarbons to form either higher orlower boiling hydrocarbons the solid particles are catalytic and themixture of coarse and fine particles is introduced into a standpipewhere it is aerated to form a fluidized mass. The fluidized mass in thestandpipe creates a pressure which is used to introduce the catalystparticles into a mixing zone where they are mixed with hydrocarbonvapors and the resulting oil-catalyst suspension is introduced into adesirable conversion zone.

In the previous form of the inventionwhere hydrocarbons are convertedcatalyticall into either higher or lower boiling hydrocarbons, thestandpipe for withdrawing catalyst particles for a hydrocarbonconversion is connected to the bottom of the main hopper. The catalystparticles are fluidized in the standpipe and then mixed with oil vaporsand passed to a conversion zone. In the last form of the inventiondescribed, the standpipe for the main hopper is eliminated and thestandpipe is associated with the electric precipitating means.

While catalytic conversion of hydrocarbons has been particularlyreferred to above, it is to be understood that my invention is not to berestricted thereto as in its broader aspects my invention may be usedfor mixing materials which cannot be aerated with coarser materialswhich can be aerated so that the resulting mixture can be aerated andformed into a fluidized mass.

In the drawing:

Figure 1 diagrammatically represents one form of apparatus for carryingout the preferred form of my invention; and

Figures 2 and 3 represent other forms of apparatus for carrying out myinvention.

Referring now to Figure 1 of the drawing, the reference character Indesignates a line for conveying regenerated catalyst .particles andregeneration gases. It is to be understood that the catalyst particleshave been previously used in a treating process during which thecatalyst particles became fouled with carbonaceous material and thiscarbonaceous material was burned on the catalyst particles in anysuitable manner. The suspension of the catalyst particles in theregeneration gases passes through the line l0 to a separating means I!of any suitable con struction. For example, a cyclone separator such asshown in the drawing may be used.

In the separating means I! there is a preliminary separation betweensolids and gases, the solids dropping into the bottom of the separatingmeans and passing through line I3 to a catalyst hopper I. The solidparticles separated in the first separating means l2 contain most of thelargest particles in the suspension.

The separated gases still contain appreciable amounts of solid particlesand are passed through line IE to a second separating means l8 of anysuitable construction. Preferably, a cyclone separator is used in thesecond separating step. The solids separated in the separating means l8drop into the bottom of the separating means and are conducted to thehopper I! by means of the depending pipe 22 which extends below thesurface 23 of the catalyst particles in the hopper H. The particlesseparated in the second separating step are of a smaller size than thoseseparated in the first separating means [2. r

The separated gases still contain appreciable amounts of solid particlesand these gases pass overhead through line 24 to a third separatingmeans 26 which may be of any suitable construction but which ispreferably an electrical precipitator, such as a Cottrell precipitator.If

another cyclone separator may be included ahead of the electricprecipitator. The separating means 26 is adapted to remove substantiallyall of the solid particles from the gaseous stream. Before being passedto the electric precipitator 26. the gaseous stream is preferably passedthrough cooler 21. The solid particles separated by the separating means26 are exceedingly fine and it has been found that these fine particlestend to bridge at the outlet from the separating means-26 and do notflow readily through a .pipe or return conduit. The separating means 26isprovided with a return conduit 28 which extends below the level 23 ofthe catalyst particles in the hopper l4.

As above pointed out, the catalyst particles separated in the lastseparating means 26 are not easily conveyed and while certain sizedsolid particles may be aerated to cause them to flow as a fluid, theseexceedingly fine .particles leaving the electrical precipitator do notreadily aerate and it has not been possible to fiuidize theseexceedingly return to the hopper l4 or other container.

I have found that these exceedingly fine particles may be more easilyconveyed and handled if they are mixed with a relatively small amount ofcoarser particles. In the specific form of the invention disclosed inFigure 1, coarser catalyst particles or solid particles are withdrawnfrom the hopper i4 through an inclined pipe 84 and fed to a mixing zone35 wherein the coarse particles are mixed with air or other suitable gasintroduced through line 36. The suspension of coarse catalyst in gas isthen passed through line 38 and is mixed with the gases leaving thesecond separating means i8 by means of line 24. The mixture of coarserparticles and relatively fine particles is introduced into theelectrical precipitator 26 and the coarse particles and exceedingly fineparticles are precipitated as a mixture. The coarse particles render themixture fiowable. Without aeration the mixture of coarse particles andfine particles flows from the precipitator 26 without bridging andwithout plugging the line 28'. In some instances the mixture may also beaerated to fluidize the mass and to cause it to fiow back to the hopperl4 more readily. It is to be noted that the catalyst or solid particleswithdrawn by line M from the hopper l4 are those catalyst particles orsolid particles near the outlet of the first separating means l2 andcomprise the larger or coarser solid particles. the gaseous streamcontaining the exceedingly fine particles, the suspension of coarserparticles acts as a scrubbing means to assist in the removal of thecatalyst or solid particles from the gases. Preferably, a slide valve 42is provided for the withdrawal pipe 34.

While Figure l of the drawing describes withdrawal of solid coarseparticles from the hopper desired.

or container l4, it is within the contemplation of the invention toclose the slide valve 42 and to introduce coarse solid particles intothe line 38 by means of line 44; or the coarse solid particles may beintroduced into the lower portion of the precipitator 26 by means of aline 46. The coarse solid particles introduced either through line 44 or46 may be the same material as the exceedingly fine solid particles orthey may be other material which is of a large size than the fineparticles and which is substantially inert with respect to the finesolid particles. The coarser particles introduced through line 44 orfine particles to facilitate their Being introduced into line '48 may beaddedas powdered material but are'preferably added as a suspension in agas. The coarse particles may be taken from pipe it from the firstcyclone and introduced into separator 26 or into line 88.

When the process used sion of hydrocarbons, l4 will be catalystparticles. Any suitabl catalyst may be used such as activated clay orsynthetic catalysts containing alumina and silica. The catalystparticles pass downwardly in the catalyst hopper l4 and are withdrawntherefrom through a line 48. In cases where the line-48 constitutes astandpipe in which the catalyst particles are maintained as a fluidizedmass, means including manifold 52 and branch lines 54, 56 and 58 areprovided for injecting a substantially inert gas such as steam into themass of catalyst in the standpipe to aerate the mass and provide afluid-like mixture. Another branch line or lines 59 is provided forfiuidizing the catalyst particles in the bottom portion of hopper l4.

The fluid-like mixture provides a head of pressure for introducing thecatalyst into a mixing zone 62 where it is mixed with hydrocarbon vais acatalytic converpors or gases introduced through line 64. The

catalyst-oil suspension is then passed to a suitable conversion zone.Preferably the bottom of standpipe 48 is provided with a valve 65 forcontrolling the outfiow of catalyst to zone 62. Fresh catalyst may beintroduced into hopper l4 by means of line 66. A line 68 is provided forremoving aeration gas from hopper l4. Line 68 communicates with line itbetween the first separating means i2 and the second separating means i8so that the removed gas is passed through separating means l8.

The exceedingly fine particles which are recovered in the electricalprecipitator 26 have a par with the fines may contain particles of asize I from about 0 microns to microns with about 70 by weight beingover40 microns.

The amount of coarser catalyst particles to be usedwith the exceedinglyfine catalyst particles is about 50% to 100% by weight of the coarsercatalyst particles with respect to the exceedingly fine catalystparticles. Where the exceedingly fine catalyst particles contain about70% of less than about 20 microns, about the same or slightly smallerproportion of coarser catalyst particles as above given may be used toprovide a mixture which flows more easily.

The form of the invention shown in Figure 2 will now be described. Solidparticles in a gaseous' suspension are passed through line 10 andintroduced into a first separating means 12 which may be a cycloneseparator. The solid particles in the gaseous suspension may be anysuspension the particles in the hopper passed through line 14 into amain hopper 16, the pipe or line 14 preferably extending below thesurface 18 of the solid particles'in the main hopper.

The gases separated in the first separating mean 12 still containappreciable amounts of solid particles and these gases are passedthrough line 82 to a second separating means 84 which may be a, cycloneseparator. In the second separator 64 smaller solid particles areseparated and are withdrawn from the bottom of the second separator 84through line 86 which extends into the main hopper 16 and below thelevel of the solid particles in the hopper.

The separated gases leaving the second separator 84 through line 88still contain solid particles which are relatively fine and a thirdseparating means may be used, if desired. To separate these fineparticles from the suspension leaving the second or third separatingmeans an electric precipitating means is used. Where the gasescontaining the fine particles are hot, the suspension may be passedthrough a cooler 92 before being introduced into the electricprecipitating means 94. In the electric precipitating means the finesolid particles are removed from the gas, the separated gas being passedthrough outlet 96.- If the gases in line 88 are cool, the cooler 92 isby-passed by means of line 91.

The solid fine particles collecting in the bottom of the electricseparating means 94 are withdrawn therefrom and introduced into astandpipe I06. As above pointed out, the fine solid particles separatedin an electric precipitating means do not flow readily and cannot beaerated or fluidized. In order to improve the flow characteristics ofthe fine solid particles, a portion of the coarser or larger solidparticles from the main hopper 16 are withdrawn from the main hopperthrough line I68 and introduced into the lower portion of the electricprecipitating means 94 for mixing the larger or coarser solid particleswith the finer particles. The line I08 is provided with a valve H2. Thecatalyst or other solid particles in the bottom of hopper 16 are aeratedor fluidized by the introduction of a fiuidizing gas such as steamthrough line II 3. A line H4 is provided for removing aerating gas fromhopper 16 and passing it to line 82 and second separator 84.

The mixture of the coarser and fine particles is introduced into thestandpipe I06 where it is aerated or fluidized by the introduction ofsteam or other suitable gas. The steam or other suitable gas isintroduced into the standpipe at spaced points through lines H5. Thebottom of the standpipe I06 is provided with a slide valve or othersuitable valve II6 for controlling the amount of solid particleswithdrawn from the standpipe I66.

From the bottom of the standpipe I06, the solid particles are suspendedin steam, or the like, introduced through line H8 and the suspension ispassed through line I22 to line 82 leading to the second separator 84and mixed with the suspension passing to the second separator 84.

The solid particles are withdrawn from main hopper 16 in any desiredmanner and transferred to any point desired. In the catalytic conversionof hydrocarbons to make either higher or lower boiling hydrocarbons thesolid particles are catalytic and are preferably withdrawn from the mainhopper into a main standpipe I32. The catalyst particles in thestandpipe I32 are fiuidized by introducing steam or other inert gas intothe standpipe through lines I arranged at suitable spaced points alongthe lentgh of the standpipe.\. The fluidized catalyst particles arewithdrawn from the bottom of the standpipe I32, the fiow of thefluidized mass from the standpipe being regulated by a slide valve orother suitable valve I34 arranged at the bottom of the standpipe. I

' The catalyst particles in fluidized form are introduced into a mixingzone I 88 wherein they are mixed with hydrocarbon vapors introduced intothe mixing zone through line I38 and the hydrocarbon catalyst mixture isthen passed to a suitable conversion zone. During conversion, thecatalyst particles become coated with carbonaceous deposits and generalpractice is to regenerate the catalyst particles, preferably by burningoff the carbonaceous deposits and the regenerated catalyst particles andregenerating gases are then treated to separate solid regenerated-catalyst particles from regenerating gases. The form of the inventionshown in Figure 2 or Figures 1 and 3 may be used for carrying out thisseparation.

A valved inlet pipe I48 is provided for main hopper 16 for introducingfresh catalyst or solid particles into the main hopper".

Referring now to the form of the invention shown in Figure 3, a gaseoussuspension of solid particles is passed through line I52 to a firstseparating means I54 fOr separating solid particles from gases. drawnfrom the separating means I54 and passed through line I56 into a hopperI58. The pipe or tube I56 extends below the surface I60 of the solidparticles in the hopper I58. Aerating or fiuidizing gas is preferablyintroduced into the bottom of hopper I58 through line I62 to fiuidizethe solid particles therein. A line I63 is provided for-removingaerating gas from the top of hopper I58 to line I64 and to secondseparating means I66.

The gases leaving the first are passed through line I64 to a secondseparating means I66 for separating additional quantities of solidparticles from gases. The separated solid particles are collected in thebottom of the separating means I66 and withdrawn therefrom andintroduced into the hopper I58 through a pipe or line I68 which extendsbelow the surface I66 of the solid particles in the hopper I58. Thegases separated in the second separating means I 66 still contain solidparticles which are finer than those separated in the first and secondstages and these gases are passed through line I12 and cooler I14 andthen introduced into an electric precipitating means I16. Anotherseparating means may be used ahead of precipitating means I 16, ifdesired. Where the gases leaving the second separating means I 66 are ata relativeiy high temperature, the cooler I14 may be used. However,where the gases are at a relativeiy low temperature, the cooler I14 mabe omitted and the gases passed through by-pass line I11. I

The electric precipitating means I16 acts to remove fine solid particlesfrom the gas and the separated gas is passed through an outlet I18. Theseparated fine solid particles accumulate in the bottom of theseparating means I16 or in a hopper below the electric precipitatingmeans separating means I16. As above pointed out, these fine particleshave very poor fiow characteristics, are difficult to aerate and tend tobridge-over in outlet passages from hoppers or other containers. Inorder to improve the flow characteristics of the fine The solidparticles are withlarge particles.

solid particles, the larger or coarse particles collected i'n hopper I58are withdrawn through line I80 having valve I8I and introduced into thebottom of the electric precipitating means I16 for mixing the fine solidparticles with the coarser or The resulting mixture is introduced into astandpipe I82 wherein the solid particles are fluidized by theintroduction of steam or other suitable inert gas through lines I86. Thesolid particles in the bottom of the precipitator I16 are preferablyfluidized by introducing fluidizing gas through line I81. The bottom ofthe standpipe I82 is provided with a slide valve or other suitable valveI88 for regulating the flow of the fluidized mass from the standpipe.

Where the form of the invention shown in Figure 3 is used for thecatalytic conversion of hydrocarbons either to higher or lower boilinghydrocarbons, the ticles and the fluidized mass is introduced into amixing zone I92 where the catalyst particles are mixed with hydrocarbonvapors or gases introduced through line I94 and the resultinghydrocarbon catalyst mixture passed to a suitable conversion zone.

Inthe form of the invention shown in Figure 3, it will be seen that thesolid particles from the hopper I58 are all introduced for admixturewith the fine particles separated in the electric precipitating meansand the resulting mixture passed to a standpipe. Comparing Figure 3 withthe apparatus shown in Figure 2, it will be seen that in Figure 2 themain catalyst hopper I6 is provided with a standpipe I32 and theelectric precipitating means 94 is provided with a standpipe whereas inthe form of the invention shown in Figure 3 there is only one standpipewhich is associated with the electric precipitating means I16, thestandpipe associated with the hopper I58 having been eliminated.

Or, in Figure 1 a portion of the coarse catalyst or other solidparticles from separator l2 passing through line I3 may be mixed withextremely fine solid particles separated in precipitator 26. Also inaddition or instead of the coarse particles from separator I2, I may usethe relatively coarse particles from the second separator l8 passingthrough line 22 and mix them with the extremely fine particles separatedin precipitator 26. In some instances it may be necessary to add ahopper under the precipitator 26 and separated therefrom by a suitablevalve to take care of difierences in the pressure of the variousstreams.

The levels of the solid particles in the pipes 22 and 28 are shown. Thisdifference in level is due to the lower pressure existing in separator26 and the head of particles in pipe 28 is necessary to return theparticles to the hopper I4. Pipe 28 is made longer than pipes 22 and I3to compensate for the lower density of the particles in pipe 28 and thegreater pressure difi'erential which must be counteracted by the head ofcatalyst.

While the drawing describes apparatus for separating solid particlesfrom a gaseous suspension thereof and mixing a part of the coarserparticles with the exceedingly fine particles separated in the lastseparating means, and while the specific form of my invention has beendescribed in connection with catalytic conversion or treatment ofhydrocarbons, it is to be expressly understood that the drawing anddescription are by way of example only and that my invention is not tobe restricted thereto but may also be used to more easily convey orhandle exceedingly fine solid particles by admixing therewith coarsersolid parsolid particles are catalyst par-4 4 l0 ticles, whereby theresulting mixture will flow through pipes more readily and will notbridge the outlets of containers or hoppers, and will in general be moreeasily handled.

Instead of using an electric precipitator as the last separating means,a cyclone separator may be used for'separating fines which are mixedwith coarser or larger particles as above described.

While my invention has specifically referred to regenerated catalystparticles suspended in regenerating gases, it is to be understood thatmy invention may also be used to separate catalyst particles fromreaction products leaving a reaction zone, such as a conversion zone.

I claim:

1. Process of maintaining a fluidized mass of finely divided solidsserving as a source of supply for a chemical reaction, comprisingcontinuously.

introducing into the mass a stream of fluidizing gas, supplying saidmass with said solids as separate streams in varying degrees ofsubdivision including particles of extreme fineness, and mixing aportion only of the particles of said solids larger than said particlesof extreme fineness with said particles of extreme fineness, prior totheir discharge to said chemical reaction, whereby the flowcharacteristics of said particles of extreme fineness are improved andthe maintenance of the mass in fluidized condition is facilitated.

2. Process according to claim 1, in which the main fluidized massreceives solids larger than said particles of extreme fineness, andsolids from said mass are passed into contact with said particles ofextreme fineness to form a separate fluidized mass.

3. Process according to claim 1, in which said particles of extremefineness are carried bya gas stream, a portion of said mass containingparticles larger than those of extreme fineness is passed into admixturewith said particles of extreme fineness, and the gas stream containingthe particle mixture is then subjected to electrical precipitation.

4. Process according to claim 1, in which the particles-of extremefineness are between about 0-20 microns in diameter.

5. Process of maintaining a fluidized mass of finely divided catalyticmaterial to be used as a source of supply of catalyst for the conversionof hydrocarbon oils, comprising continuously introducing into the massof catalyst a stream of fiuidizin gas, recovering catalyst carried offby said gas, supplying said mass with separate streams of said recoveredcatalyst in various degrees of subdivision including particles ofextreme fineness, and mixing a portion only of said catalyst from saidmass, containing particles larger than those of extreme fineness, withsaid particles of extreme fineness at a point adjacent their point ofseparation and prior to their dis charge to said process of hydrocarbonconversion, whereby the flow characteristics of said particles ofextreme fineness are improved and the maintenance of the mass influidized condition is facilitated.

6. In the recovery of catalyst of the finely divided type adapted foruse in fluidized condition for the conversion of hydrocarbon oils, theimprovement which comprises passing the catalyst suspended in a gasiformfluid through a series of catalyst separating zones, passing into acollecting zone separated catalyst in progressively finer condition fromeach of said separating zones, the catalyst from. the last separatingzone being of extreme fineness, maintaining catalyst in said collectingzone in fluidized condition, and mixing a small portion only of the"catalyst from said collecting zone with the extremely finely dividedcatalyst separated in the last of said series of separating zones, saidmixing being-eifected at a point adjacent the point'of separation ofsaid particles of extreme fineness and outside said collecting zone, toimprove the flow characteristics of said particles of extreme finenessprior to passing them into the collecting zone.

7. Process of maintaining a fluidized mass of finely divided solids in acollectin zone, comprising continuously introducing into the mass astream of fiuidizing gas, recovering in a plurality oi stages finelydivided solids carried from the mass by said gas, the particlescollected in the last of said plurality of stages being in extremelyfinely divided condition, returning as such to the mass of fluidizedsolid the finely divided solids recovered in the first of said pluralityof stages, continuously withdrawing from said mass of fluidized solids apart only thereof containingparticles of larger size than the extremelyfinely divided particles collected in the last of said plurality ofstages, commingling said part with said extremely finely dividedparticles adjacent the point of separation of the latter, and passingthe resulting flowable mixture of particles from a point outside thecollecting zone through a conduit and into said zone at a point spacedfrom the point of withdrawal of said part of the fluidized mass.

8. Process of maintaining a, fluidized mass of finely divided solids ina collecting zone, comprising continuously introducing into the mass astream of fiuidizing gas, recoverin in a plurality of stages finelydivided solids carried from the mass by said gas, the particlescollected in the last of said plurality of stages being in extremelyfinely divided condition, returning as such to the mass of fluidizedsolid the finely divided solids recovered in the first of said pluralityof stages, continuously commingling solid particles of larger size thanthe extremely finely divided particles collected in the last of saidplurality of stages with said extremely finely divided particlesadjacent the point of separation of the latter, and passing theresulting flowable mixture *of particles from a point outside thecollecting zone through a conduit and into said collecting zone.

9. In the recovery of catalyst of the finely divided type adapted foruse in fluidized condition for the conversion of hydrocarbon oils, theimprovement which comprises passing the catalyst suspended in a gasiformfluid through a series of catalyst separating zones, passing into acollecting zone separated catalyst in progressively finer condition fromeach of said separating zones, the catalyst from the last separatingzone bein of extreme fineness, and mixing catalyst comprising coarserparticles with the extremely finely divided catalyst separated in thelast of said series of separating zones, said mixing being effected at apoint adjacent the point of separation of said particlesof extremefineness and outside said collecting zone, to improve the fiowcharacteristics of said particles of extreme fineness priorto passingthem into the collecting zone.

10. In a process for recovering finely divided catalyst of varyingparticle sizes from a gas stream leaving a contactin zone, theimprovement which comprises passing the catalyst suspended in a gasstream through at least one sepa- 12 rating zone capable of separating arelatively coarse traction of said catalyst from said gas stream,thereafter passing the gas stream containing the remaining portioncomprising relatively fine catalyst through a final separating zonecapable of separating a fine fraction of catalyst therefrom, intermixingrelatively coarse catalyst initially separated from said gas stream withthe fine traction separated in the final separating zone immediatelyadjacent the point of separation 01' the fine .iraction, maintaining avertical column of said intermixture of catalyst particles of a heightsumcient to develop a pressure at the base oi said column at leastsufilcient to restore the pressure lost during passage of said gasstream through said separating zones, adding said intermixture ofcatalyst particles to the top of said column and discharging saidintermixture from the base of said column at an increased pressure forreturn to said contacting zone. 7

11. In the recovery of catalyst or the finely divided type adapted foruse in fluidized condition for the conversion of hydrocarbon oils, theimprovement which comprises passing the catalyst suspended in-a gasiformfiuid through a series of catalyst separating zones, passing into acollecting zone separated catalyst in progressively finer condition fromeach of said separating, zones, the catalyst from the last separatingzone being of extreme fineness, and mixing a small portion only of thecatalyst from said collecting zone with the extremely finely dividedcatalyst separated in the last of said series of separating zones, saidmixing being effected at a point adjacent the point of separation ofsaid particles of extreme fineness and outside said collecting zone, toimprove the fiow characteristics of said particles of extreme finenessprior to passing them into the collecting zone.

'12. In a system for the regeneration of finely divided catalystparticles by burning contaminants therefrom and separating regeneratedcatalyst particles from the regeneration gases, the steps which comprisepassing a stream of hot regenerated catalyst suspended in regenerationgases through at least one separating zone capable of separating arelatively coarse fraction of said catalyst from said gas stream,thereafter cooling the gas stream containing the re maining portion ofcatalyst particles comprising relatively fine catalyst and passing thecooled stream through a final separating zone capable of se arating aflne fraction of catalyst therefrom, intermixing the relatively hotcoarse catalyst initially separated from said gas stream with the cooledfine catalyst fraction separated in the final separating zoneimmediately adjacent the point of separation Of the fine fraction,maintaining a vertical column of said intermixture of a heightsuificient to develop a pressure at the base of said column at leastsufilcient to restore the pressure lost during passage of said gasstream through said separating zones, adding said admixture to the topof said column and discharging said intermixture from the base of thecolumn for return to the system.

13. In a system for the regeneration of finely divided catalystparticles by burning contaminants therefrom and separating regeneratedcatalyst particles from the regeneration gases, the steps which comprisepassing a stream of hot regenerated catalyst suspended in regenerationgases through at least one separating zone capable of separating arelatively coarse fraction Of said catalyst from said gas stream, there-I after cooling the gas stream containing the remaining portion ofcatalyst particles comprising relatively fine catalyst and passing thecooled stream through a final electric precipitation zone capable ofseparating a fine fraction of catalyst therefrom, intermixing therelatively hot coarse catalyst initially separated from said gas streamwith the cooled fine catalyst fraction separated in the final separatingzone immediately adjacent the point of separation of the fine fraction,maintaining a vertical column of said intermixture of a heightsuflicient to develop a pressure at the base of said column at leastsufiicient to restore the pressure lost during passage of said gasstream through said separating zones, adding said admixture to the topof said column and discharging said intermixture from the base of thecolumn for return to the system.

14. Process of maintaining a fluidized mass of finely divided catalyticmaterial to be used as a source of supply of catalyst for the conversionof hydrocarbon oils, comprising continuously introducing into the massof catalyst a stream of fiuidizing gas, supplying said mass withcatalyst in varying degrees of subdivision including relatively largeparticles and particles of exnants therefrom and separating regeneratedcatalyst particles-from the regeneration gases,

. the steps which comprise passing a stream of treme fineness,recovering in a plurality of separating stages and as separate streamscatalyst carried off by said gas, the catalyst separated in the firststage comprising larger particles than those of extreme finenessrecovered in the last stage and being returned to said mass as aseparate stream, mixing a portion only of said catalyst from said masscontaining particles larger than those of extreme fineness with saidparticles of extreme fineness at a point adjacent their point ofseparation prior to their discharge to said process of hydrocarbonconversion whereby the flow characteristics of said particles of extremefineness are improved.

15. In a system for the regeneration of finely divided catalystparticles by burning contamihot regenerated catalyst suspended inregeneration gases through at least one separating zone capable ofseparating a relatively coarse fraction of said catalyst from said gasstream, thereafter cooling the gas stream containing the remainingportion of catalyst particles comprising relatively fine catalyst andpassing the cooled stream through a final electric precipitation zonecapable of separating a fine fraction of catalyst therefrom, intermixingrelatively hot coarse catalyst initially separated from said gas streamwith the cooled fine catalyst fraction separated in the final separatingzone immediately adjacent the point of separation of the fine fractionand returning said intermixture to the system.

ROBERT W. KREBS.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,298,409 Schmidt Mar. 25, 19191,446,778 Witte Feb. 27, 1923 1,508,331 Huber Sept. 9, 1924 1,553,539Kinyon Sept. 15, 1925 1,970,405 Thomas Aug. 14,1934 1,997,125 Soyez etal. Apr. 9, 1935 2,037,090 Pough Apr. 14, 1936 2,231,424 Huppke Feb. 11,1941 2,273,075 Weems, 3rd Feb. 17, 1942 2,302,209 Goddin, Jr. Nov. 1'7,1942 2,302,328 Kelly Nov. 17, 1942 2,322,019 Hemminger June 15, 19432,325,516 Holt et al. July 27, 1943 2,326,705 Thiele et al. Aug. 10,1943 2,337,684 Scheineman Dec. 28, 1943 2,347,682 Gunness May 2, 19442,373,008 Becker Apr. 3, 1945

1. PROCESS OF MAINTAINING A FLUIDIZED MASS OF FINELY DIVIDED SOLIDSSERVING AS A SOURCE OF SUPPLY FOR A CHEMICAL REACTION, COMPRISINGCONTINUOUSLY INTRODUCING INTO THE MASS A STREAM OF FLUIDIZING GAS,SUPPLYING SAID MASS WITH SAID SOLIDS AS SEPARATE STREAMS IN VARYINGDEGREES OF SUBDIVISION INCLUDING PARTICLES OF EXTREME FINENESS, ANDMIXING A PORTION ONLY OF THE PARTICLES OF SAID SOLIDS LARGER THAN SAIDPARTICLES OF EXTREME FINENESS WITH SAID PARTICLES OF EXTREME FINENESS,PRIOR TO THEIR DISCHARGE TO SAID CHEMICAL REACTION, WHEREBY THE FLOWCHARACTERISTICS OF SAID PARTAICLES OF EXTREME FINENESS ARE IMPROVED ANDTHE MAINTENANCE OF THE MASS IN FLUIDIZED CONDITION IS FACILITATED.